pibase Extension not working after Upgrade to TYPO3 9

Question

I'm currently upgrading an old TYPO3 6.2 Installation to 9.5. I'm also using fluidtypo3 (flux 9.3.2 and fluidpages 5.0.0). There are several pibase Extensions, that I can't get to work. One of them has the following error:

Oops, an error occurred! Code: 20200320122044742c5a45 - {"exception":"TYPO3Fluid\\Fluid\\Core\\ViewHelper\\Exception: No Content Object definition found at TypoScript object path \"tt_content.list.20.edxdownload_pi1\"

Any hints what is causing the error? Did I forget anything to register?

I added the plugin in tt_content.php, registered it in localconf.php

(\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addPItoST43('edx_download','','_pi1','list_type',0);)

and added the config in sys_template.php

(TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addStaticFile('edx_download','Configuration/TypoScript/PluginSettings/', 'Edx Download Settings');)

If I make a new element using the new element wizard, I get the following error in frontend:

Content Element with uid "9887" and type edx_download_pi1 has no rendering definition!

Where do I have to set the rendering definition?

Do pibase extensions still work with TYPO3 9?

Edit: It's working now. I put the method "addPItoST43" back into "ext_localconf.php" and now the extension is loaded. It says you should put it into "TCA/Overrides/tt_content.php", but that doesn't work for me with TYPO3 9.5.